Abstract: :
Purpose: To set criterias for the evaluation of image qualityof digital non-mydriatic retinal images, and evaluate photographsobtained with and without mydriasis using the same digital camera.Methods: 83 patients with either type 1 or type 2 diabeteswere recruited at The Steno Diabetes Center based on medicalrecords. All patients were photographed with and without mydriasisusing a TOPCON TRC-NW6S non-mydriatic digital fundus camerainterfaced with a JVC 3CCD color camera with a pixel resolutionof 1450 x 1062. Five overlapping 45° images (posterior pole,nasal, temporal, superior and inferior) were captured of eacheye, and using an IMAGEnet 2000 computer system the images weremerged into a single mosaic image and stored in TIF format.Image quality was then evaluated by two ophthalmologist basedon the criterias listed in tabel 1.Results: The quality ofall images captured with mydriasis were evaluated as being eitherexcellent or good (tabel 1), blur due to cataract being theprimary reason why not all mydriasis images were evaluated asbeing excellent. The quality of the images captured withoutpupildilation were evaluated as listed in tabel 1. As the non-mydriaticcamera has as a requirement, that the pupil diameter is to begreather then 4 mm to obtain an adequate image quality, it wasnot surprising that the primary reason for undilated imagesto be evaluated as being either poor or ungradable were dueto the pupildiameter being < 4 mm. This was shown to be highlyage related (P<0.001 Χ2trend). Thus non among the 20-29 yearold had a pupil diameter < 4 mm, 7 % of the 30-39 year old,12 % of the 40-49 year old, 16 % of the 50-59, 62 % of 60-69year old and 100 % of the 70-79 year old had a pupil diameter< 4 mm. Cataract did not influence the evaluation of undilatedimages substantially.Conclusion: When using a nonmydriaticdigital camera in screening for diabetic retinopaty approximately1 out of 5 will require mydriasis. Table 1. Criterias and distribution of image quality